in file Handler.php, method WURFL_Handlers_Handler::getPrefix() Returns the prefix for this Handler, like BLACKBERRY_DEVICEIDS for the BlackBerry Handler. The "BLACKBERRY_" portion comes from the individual Handler's $prefix property and "_DEVICEIDS" is added here.

in file Filter.php, class WURFL_Handlers_Filter WURFL_Handlers_Filter is the base interface that concrete classes must implement to classify the devices by user agent and then persist the resulting datastructures.